function findListK(head, k) {
    if (!head || k < 0) {
        return null
    }

    let headA = head;
    let headB = head;

    while (k) {
        if (headA.next) {
            headA = headA.next;
            k--
        } else {
            return null
        }
    }

    while (headA) {
        headA = headA.next;
        headB = headB.next
    }

    return headB
}